1. Field of the Invention
This invention relates to hollow core concrete building panels, which are utilized as walls, ceilings, floors, roofs, columns and the like, and specifically to improved methods of manufacturing, installing and providing load bearing structure for said panels.
2. Description of Prior Art
The desirability of hollow core concrete building panels is well known. The lighter weight allows the construction of larger panels, reduces transportation costs, and permits the use of smaller handling equipment. Furthermore, the hollow core area is ideal for insulating materials as well as a way to decrease the amount of concrete necessary for a structurally sound panel.
There are basically two types of hollow core concrete panels in use and distinguished by the manufacturing process and the type of connection between the two skins. The first type of panel has a concrete connection between the skins and is monolithically cast using special formwork to create the hollow core area. The second type of panel consists of two, separately cast skins, which are connected by an elaborate wire or metal structure to facilitate the creation of the hollow core area.
These existing hollow core concrete panels have a variety of limitations that adversely affect their cost, finished appearance and flexibility. For example, the monolithically cast panels allow for only a single side to be horizontally cast in a form liner mold which leaves the second face roughly finished and in need of additional work. Furthermore, to create the hollow core area for the monolithic panel, the manufacturing process requires extensive internal forms, which are either left in place or provided by expensive and cumbersome equipment, both of which increases the panel's cost.
Those hollow core panels composed of separately cast skins are held together by extensive fabricated wire or metal structures that substantially add to the cost. Due to the weight of the individual skins and the tenuous connections, these panels are prone to shifting unless they are welded, have additional supports, and utilize an over abundance of wire. Furthermore, one variation of this panel requires the hollow core area to be filled with a cementitious or other solid material after it has been placed at the job site in order to provide the panel with permanent stability and the necessary structural support. In other panel design variations, thicker skins are required and another material layer is added during manufacturing to act as forming for the hollow core area. However, because of the additional requirements, neither of these panel designs provide for any real material savings over conventional methods.
In all cases, the thickness of the panel skin is dependent upon the type of structural forces to which it is subject. These panels are typically designed for load bearing purposes which require a thicker prefabricated skin than necessary to withstand only lateral forces. Therefore, the thicker skins required by the these existing hollow core panels require more concrete and reinforcement material which in turn increases the panel's cost and weight and makes handling more difficult.
The existing hollow core panels offer little flexibility in terms of customizing their structural integrity and material requirements for different applications. In certain situations, the handling method requires the panel to have greater structural strengths than are necessary for the application intended. Thus, in many instances, these panels contain much more material and structural strength than is needed for the particular application. This causes the panels to be uneconomical replacements for conventional materials and methods.
Finally, most of the existing concrete building panels require a continuous foundation which offers no advantage over conventional construction. Furthermore, many of these panels are difficult to integrate into a typical building project and require additional steps such as welding to connect them with other materials. These additional steps makes them less desirable or uneconomical for many building applications and projects.